High power double slug tuner



March 29, 1955 M VAN-|- HIGH POWER DOUBLE SLUG TUNER 2 ShetS-Sheet l Filed Aug. 4, 1953 ATTURNEY March 29, 1955 1 M, VAN-r 2,705,306

HIGH POWER DOUBLE SLUG TUNER Filed A ug. 4. 1953 2 Sheets-Sheet 2 AITTURNEY United States Patent O HIGH POWER DOUBLE SLUG TUNER Leslie M. Vant, Natick, Mass., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Army Application August 4, 1953, Serial No. 376,485

1 Claim. (Cl. 333-98) This invention relates to an improved means for varying a characteristic of a pressurized wave guide, and more particularly to an improved means for varying the tuning of a pressurized wave guide.

It is an object of the present invention to provide a novel and improved apparatus for adjusting the position of a movable element within a wave guide while the wave guide remains under pressure.

A further object of this invention is to provide an ap paratus for positioning a movable element within a pressurized wave guide from a point outside the wave guide, while maintaining a ow of air through the wave guide.

Pressurized wave guides to which this invention is applicable are provided with apertures in the wall thereof to permit a continuous flow of gas within the guide. In accordance with this invention these apertures 'are utilized as entrance points for a cable or other linkage. for connecting anadjusting mechanism outside the wave guide to an adjustable element within said wave guide.

The features of my invention which I believe to be novel are set forth with particularity in the appended claim. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawing in which:

Fig. l is a longitudinal cross-sectional view of a wave guide section which illustrates the wafer tuning slug assembly and the means for moving the assembly;

Fig. 2 is a plan view of the bottom of the wave guide section shown in Fig. l;

Fig. 3 is a cross-sectional view along the line 3, 3 of the section of Fig. l;

Fig. 4 is an elevational view of a magnetron, wave guide tuning section and load; and

Fig. 5 is an enlarged perspective view of the dielectric rods shown in Fig. l for moving one tuning slug with respect to the other tuning slug.

Referring now to Figures 1, 2, 3 and 5, there is shown a rectangular wave guide section having upper and lower walls 1l and 12, respectively. Within the wave guide is a dielectric carriage 13, 14; which may be `made of teon or any other suitable dielectric material. Fixedly mounted in the carriage is a first wafer tuner slug 17. Adjustably mounted in grooves 15, 16 in the carriage is a second wafer tuner slug 18. The tuner slugs are shown as metal slugs and may be silver plated brass, however, it is understood that in certain tuners, it may be preferable to use dielectric slugs instead of metal slugs. Dielectric mooring posts 19 and 20 for cable 33 are mounted at each end of carriage member 14.

ln the wall 12 of the wave guide section there are two apertures 25 and 26. Over these apertures are metal plates 21 and 22 which are slotted and serve as mountings for pulleys 23 and 24. Element 27 is an idler pulley mounted on plate 28, which has a slot 29 to allow movement of said plate with respect to pins 30. To maintain constant tension on the idler pulley and thereby maintain taut cable 33, there is provided a spring 31 fastened at one end to plate 28 and at the other end to metal support member 47 projecting from the bottom of the wave guide section. Pulley 32 is connected through a shaft to a knurled knob 34, which drives said pulley. Drive cable 33 passes over pulleys 23, 27, 32, 37, 38 and 24. Gear chain 39 which connects a gear 50 on the shaft running from knob 34 with another gear 49 on the shaft leading to pulley 37 enables knob 34 simultaneously to rice drive pulleys 32 and 37. This takes up all slack in the cable 33. ln order to indicate the position. of the carriage there is provided a scale and pointer 36 mounted on the drive cable. Metal members 47 and 48 serve as mounts for the various pulleys and the scale.

Within the guide, means are provided for moving the movable slug 18 with respect to the tixed slug 17. These include dielectric rods 40, 41 fastened to members 13 and 14 of the carriage, respectively, and dielectric rods 42 and 43, which extend adjacent rods and 41 and are fastened to tuner wafer 18. As shown in Fig. 5, at least one of -the rods may have a scale mounted or inscribed thereon to permit quick measurement of the spacing between the slugs. Normally, fixed rods 40 and 41.would have such a scale.

In order to adjust the position of slug 18 with respect to slug 17, it is merely necessary to move rods 42 and 43 with respect .to rods 40 and 41. Once the slugs have been adjusted to the desired position, sleeves 44, 45 may be slid over wedges 46 and 58 in order to maintain the desired position fixed.

The apertures 25, 26 are slightly larger than the diameter of the drive cable 33 and this permits escape of a slight amount of the pressurized gas from within the wave guide. There is, therefore, a constant flow of pressurized gas within the wave guide and this ow of gas may be used to advantage, as will be explained more fully in connection with Fig. 4.

The theory of the double slug tuner such as above described is well known, and is discussed in section 8.12 of volume 9 of Radiation Laboratory Series, titled "Microwave Transmission Circuits, by Ragan.

Fig. 4 illustrates an application of the invention to an apparatus for measuring the characteristics of a magnetron, as for example in making pulling measurements or Rieke diagrams. ln operation, a source of compressed air or any other suitable gas is connected to the pressure hose connection 51 at the end of the tuning section l0. As explained above, apertures 25, 26 allow some of the gas to escape and this permits a continuous llow of gas through the wave guide section 10. If it is desired to increase this flow of gas, a bleeder valve on the gas bleeder pressure meter assembly 54 may be opened. The combined effect of the open bleeder valve and the apertures in the wave guide is to cause any desired flow of gas through the wave guide section 10. As can be seen, pressure hose connection 5l is mounted in the guide at an angle. The ow of gas from connection 51 is pointed at the center of the magnetron ceramic window and it serves to cool the window and surrounding magnetron parts.

Load 55 is a water load within a rectangular section of wave guide. It is similar to the apparatus illustrated on page 199 of volume l1 of the Radiation Laboratory Series, titled Technique of Microwave Measurements by Montgomery. Coupling 57 may be the water inlet and coupling 56 the water outlet. 53 is an R. F. sampling probe connection point. The measurement of power output by water loads is well known in the art and is described fully in section 3.32-337 of the aforesaid volume 1l of the Radiation Laboratory Series.

To obtain a typical power measurement by using the setup illustrated in Fig. 4, a source of water is connected to the inlet 57 and a source of gas under pressure to the connection 5l. The bleeder valve 54 is then adjusted, if necessary, to provide the proper ow of gas through the wave guide assembly and high voltage applied to the magnetron 52. When the desired power level is reached at which pulling measurements are to be made, the magnetron current is held constant and the position along the wave guide of the two pulling slugs shifted by turning knob 34 which causes cable 33 to move over the various pulley wheels and transmit motion to the teon carriage. The carriage position is indicated by the scale 35 and the pointer 36.

When a complete half wave is traversed by the slug carriage, the magnetron high voltage is shfut off, the gas is shut off, and the load section 55 decoupled from the tuning section 10. The tuning knob 34 is then rotated so as to bring the slug carriage nearest the load end. In this position the dielectric rods will project from the end of the wave guide. By reference to calibration charts, the proper scale setting is found for the next pulling voltage standing wave ratio a-t the operating frequency and after unlocking the rods by moving back the dielectric locking sleeves 44, 45, the spacing between the two slugs may be adjusted to the desired setting and the sleeves locked to the rods again. The load may then be recoupled to section 10 and another run, as described above, may be made on the magnetron at the new voltage standing wave ratio. lt is suggested that after setting the slug spacing, the slug carriage be moved back down the wave guide away from the load end until the scales are com pletely inside the section 10. This avoids the possibility of breakage of `the rods by the load section at it is brought into position.

By using the apparatus described above, it has been found possible to measure frequency pulling and magnetron peak power at power levels up to 6 megawatts.

Although, in the description above, the present invention has been applied to test equipment, it will be appreciated that there are many other uses possible. For example, wave guide section l0 may be coupled between a magnetron and an antenna loal and used for matching' the magnetron to the load.

While there has been described what is at present consdcred a preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is aimed in the appended claim' to cover all such changes and modifications a's fall within Y the true spirit and scope of the invention.

I claim:

In a section of rectangular wave guide containing a gas under pressure and having a movable element therein for tuning said guide; said element comprising a pair of wafer tuner slugs mounted on a dielectric carriage mov- .jin-l the same wall thereof acting as escape vents for said gas to permit a ow of said gas through said section, one of said apertures being close to one end of said section and the other close to the other end of said section, a pulley mounted adjacent each of said apertures externally of said guide, a cable connected at one end to one end of said carriage, said cable passing through the aperture in said section closest to said end of said carriage, over the pulley in said last-named aperture, over the pulley in said other aperture, through said other aperture, and said cable being connected at its other end to the other end of saidcarriage, and means external of said section coupled to said cable at a portion thereof intermediate the ends thereof for driving said cable and maintaining it taut.

References Cited in the file of this patent UNITED STATES PATENTS Schaper Apr. 4, 1950 OTHER REFERENCES Microwave Transmission Circuits, vol. 9, Radiation Laboratory Series; McGraw-Hill Book Co., Inc.; pages 494-498. Copy in Div. 69. 

